1. Field of the Invention
The present invention generally relates to integrated circuits and, more specifically, to the non-volatile storage in an integrated circuit of a coding set on manufacturing of this circuit.
An example of application of the present invention relates to non-volatile read-only memories (ROM). Another example relates to logic interconnects within an integrated circuit.
2. Discussion of the Related Art
In many cases, there is a need to definitively code, on manufacturing of the integrated circuit, digital words in a memory or logic states conditioning the circuit operation. For this purpose, a ROM-type memory in which the coding is performed by interconnecting the drain and source of transistors forming the memory cells is generally used, so that the state read from the cell depends on the presence of this connection. The first metallization level of the structure is generally used to perform this programming.
A disadvantage of such a programming is that it is visible by analysis of the mask for forming the interconnection level, for example, by restoring of this mask from a circuit (reverse engineering).